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Thallium (Tl)

From Wikipedia, the free encyclopediaThallium is a chemical element with symbol Tl and atomic number 81. This soft gray post-transition metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air.

Thallium in the periodic table

Atomic number81
Element categoryPost-Transition Metal

Physical properties

Phase at STPSolid
Density11.85 g/cm3
Atomic weight204.38 u
Melting point577 K
303.85 °C
578.93 °F
Boiling point1746 K
1472.85 °C
2683.13 °F

Atomic properties

Electronegativity (Pauling Scale)1.62
Electron affinity36.4 kJ/mol
Oxidation states−5, −2, −1, +1, +2, +3
(a mildly basic oxide)
Ionization energies
1589.4 kJ/mol
2 1971 kJ/mol
3 2878 kJ/mol

Electron configuration

Elektronkonfiguration (shorthand)[Xe] 4f14 5d10 6s2 6p1
Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p1
Electrons per shell2, 8, 18, 32, 18, 3


Discovered byWilliam Crookes
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